User blog comment:DarkSlayer 3/Theories/@comment-7738747-20130723071503

It is confirmed in this book Nero is Vergil's son.It still doesn't say who is his mother.It is under his bio.

http://www.amazon.co.jp/exec/obidos/ASIN/4862333907/00-00-11-11-22/ref=nosim/

I guess it is rougly translated Devil May Cry 3,1, 4, 2 Artbook and it was launched in last March.

Rumours says it will be translated to english.